I installed an Ektalite screen (fresnel) in my Century. While I can't say that this makes a dramatic difference, it does seem to help at the edges and corners, and in general the gg seems more evenly lit than before. OTOH, it will introduce those fine lines into the view, especially noticeable when using a loupe. I guess if I had to do it over again, it would be a toss-up.

There is/was(?) an outfit that offered custom-fit fresnel screens for many current production cameras; some of those screens may fit the Graphics. They were fairly pricey. I had the name and URL of the firm bookmarked at one time, but I've lost it. Perhaps other members can help. There was also a member of the board who was making and selling ground glass, cut to dimension. His prices were very reasonable, and the gg's are very bright and clean; I bought four for my Century, enough to install one and have spares when needed, and I'm glad I did, because the maker had to give it up for health reasons, IIRC. But this info won't do you any good, I'm afraid.

The B&H catalog used to list fresnels for the LF field and view cameras; don't know if they're in their current listings.

There have been a number of threads on the board over the years dealing with correct mounting of a fresnel relative to the gg, and there is an article, accessible from the main page, about fresnels in general: http://graflex.org/articles/sanz-cervera/. HTH

Remove the ground glass from the mount frame.
Using your finger tips only wash both sides with warm water and dish soap. I use Dawn and apply it direct to the ground glass. Rub both sides thoroughly then holding by the edges only rinse in running water then in a pan of water with 3 to 6 drops photoflow or similar. Stand on edge and allow to air dry or dry with a lint free cloth.

A fresnel (ektalite field screen) can be washed in the same fashion but rub the ribbed side in the direction of the ribs only.

Average improvement is 1/2 to 1 stop brighter._________________The best camera ever made is the one that YOU enjoy using and produces the image quality that satifies YOU.

I cleaned both the ground glass and the Fresnel as suggested, and it did help. Funny thing is, I knew about this a hundred years ago, but I had to be reminded, probably because I knew about it a hundred years ago.